Wheelchair suspension

ABSTRACT

A wheelchair includes a pivoting drive assembly having a drive wheel, a motor drive connected to the drive wheel, and a first pivoting linkage fixedly attached to the motor drive. The pivoting drive assembly is pivotally coupled to a frame at a first frame pivot axis such that the drive wheel, motor drive, and first pivoting linkage pivot about the first frame pivot axis as a unit. The wheelchair further includes a second pivoting linkage and a front caster assembly. The second pivoting linkage is pivotally coupled to the frame at a second frame pivot axis. The first pivoting linkage is pivotally coupled to the front caster assembly at a first front caster pivot axis and the second pivoting linkage is pivotally coupled to the front caster assembly at a second front caster pivot axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 11/429,687, filed May 8, 2006 and titled “WheelchairSuspension” which is a continuation of U.S. patent application Ser. No.10/762,977, filed Jan. 22, 2004 and titled “Wheelchair Suspension”, nowU.S. Pat. No. 7,055,634, issued Jun. 6, 2006, which is a continuation ofpending U.S. patent application Ser. No. 09/974,348, filed Oct. 10, 2001and titled “Wheelchair Suspension”, now U.S. Pat. No. 7,040,429, issuedMay 9, 2006, the disclosures of which are fully incorporated byreference herein in their entirety.

FIELD OF THE INVENTION

The invention relates generally to conveyances and, more particularly,to wheelchair suspensions.

BACKGROUND OF THE INVENTION

Wheelchairs are an important means of transportation for a significantportion of society. Whether manual or powered, wheelchairs provide animportant degree of independence for those they assist. However, thisdegree of independence can be limited if the wheelchair is required totraverse obstacles such as, for example, curbs that are commonly presentat sidewalks, driveways, and other paved surface interfaces.

In this regard, most wheelchairs have front and rear casters tostabilize the chair from tipping forward or backward and to ensure thatthe drive wheels are always in contact with the ground. One suchwheelchair is disclosed in U.S. Pat. No. 5,435,404 to Garin. On suchwheelchairs, the caster wheels are typically much smaller than thedriving wheels and located both forward and rear of the drive wheels.Though this configuration provided the wheelchair with greaterstability, it made it difficult for such wheelchairs to climb overobstacles such as, for example, curbs or the like, because the frontcasters could not be driven over the obstacle due to their small sizeand constant contact with the ground.

U.S. Pat. No. 5,964,473 to Degonda et al. describes a wheelchair havingfront and rear casters similar to Garin and a pair of additional forwardlift wheels. The lift wheels are positioned off the ground and slightlyforward of the front caster. Configured as such, the lift wheels firstengage a curb and cause the wheelchair to tip backwards. As thewheelchair tips backwards, the front caster raises off the ground to aheight so that it either clears the curb or can be driven over the curb.

U.S. Pat. No. 6,196,343 to Strautnieks also describes a wheelchairhaving front and rear casters. The front casters are each connected to apivot arm that is pivotally attached to the sides of the wheelchairframe. Springs bias each pivot arm to limit the vertical movementthereof. So constructed, each front caster can undergo vertical movementwhen running over an obstacle.

SUMMARY OF THE INVENTION

The present invention relates to a wheelchair. The wheelchair includes apivoting drive assembly having a drive wheel, a motor drive connected tothe drive wheel, and a first pivoting linkage fixedly attached to themotor drive. The pivoting drive assembly is pivotally coupled to a frameat a first frame pivot axis such that the drive wheel, motor drive, andfirst pivoting linkage pivot about the first frame pivot axis as a unit.The wheelchair further includes a second pivoting linkage and a frontcaster assembly. The second pivoting linkage is pivotally coupled to theframe at a second frame pivot axis. The first pivoting linkage ispivotally coupled to the front caster assembly at a first front casterpivot axis and the second pivoting linkage is pivotally coupled to thefront caster assembly at a second front caster pivot axis.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings which are incorporated in and constitute apart of the specification, embodiments of the invention are illustrated,which, together with a general description of the invention given above,and the detailed description given below, serve to example theprinciples of this invention.

FIG. 1 is a perspective view of a wheelchair incorporating thesuspension of the present invention.

FIG. 2 is an exploded perspective view of certain components of thewheelchair of FIG. 1.

FIG. 3 is an exploded detail view of certain components of a side frameassembly of the present invention.

FIG. 4 is a side elevational view of the side frame assembly understatic conditions.

FIG. 5 is a side elevational view of the side frame assembly traversingan obstacle by ascending an obstacle.

FIG. 6 is a side elevational view of the side frame assembly traversingan obstacle by descending the obstacle.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENT

The present invention provides a wheelchair and suspension fortraversing obstacles and rough terrain. The present inventionfacilitates the traversing of obstacles and rough terrain by allowingfor the vertical and lateral movement of one or more front casterassemblies coupled to the wheelchair.

Referring now to FIG. 1, a perspective view of a wheelchair 100 of thepresent invention is shown. Wheelchair 100 is preferably a mid-wheeldrive or rear-wheel drive wheelchair. As shown, wheelchair 100 has achair 102 having arm supports 104 and 106. A control device such as, forexample, a joystick controller 108 is attached to the chair 102 forcontrolling any power-related aspects of wheelchair 100. Wheelchair 100further has removable decorative shrouds 110 covering the wheelchair'ssuspension, drive, and control systems. Projecting forward from theshrouds 110 is footrest 112 for supporting the feet of the wheelchair'suser.

Illustrated in FIG. 2 is an exploded perspective view of certaincomponents of wheelchair 100. The suspension system has a sub-frame 200for accommodating, among other things, removable batteries 226 and 228.Removably attached to sub-frame 200 are first and second side frameassemblies 202 and 204. Side frame assemblies 202 and 204 are removablyattached to sub-frame 202 via interfaces preferably in the form ofspring loaded hooks and latches. The spring loaded hooks preferablyreside on sub-frame 200 with the corresponding latches residing onside-frame assemblies 202 and 204. In this manner, an individual canmanually without the use of tools take apart wheelchair 100 for easytransportation in, for example, the trunk of a car or other largevehicle.

Each side frame assembly has at least one drive assembly having a motordrive 210 and 212 and a drive wheel 206 and 208. Each motor drive 210and 212 preferably has either a motor/gear box combination or abrushless, gearless motor. Each side frame assembly further has at leastone front caster assembly 218 and 220 coupled thereto via pivotingassemblies 214 and 216. At least one rear caster assembly 222 and 224are also provided for each side frame assembly. Each of the side frameassemblies are identical in construction and, hence, the presentdiscussion will focus on describing side frame assembly 202 with theunderstanding that such discussion is equally applicable to side frameassembly 204.

Referring now to FIG. 3, an exploded detailed perspective of certaincomponents of side frame simply 202 is shown. In this regard, side frameassembly 202 has a side frame member 301 having sub-members 302, 304,306, and 318. These side frame sub-members are preferably tubular (i.e.,circular, oval, or rectangular in cross-section) and formed and weldedtogether has shown. Pivoting assembly 214 has a first pivoting linkage319 defined by sub-linkages 320, 322, 324, and 326. These sub-linkagesare also preferably tubular in configuration, as described above, andformed and welded together as shown. Sub-linkage 326 has a motor driveassembly mounting bracket 328 attached thereto. A second pivotinglinkage 334 is also provided. As shown in FIG. 3, the overall length ofthe first pivoting linkage 319 is greater than the overall length of thesecond pivoting linkage 334. As will be presently described, thisconfiguration facilitates, for example, the dual functions of liftingand retracting the front caster assembly 335 away from the obstacle tobe traversed and inward toward the wheelchair.

The first pivoting linkage 319 is pivotally coupled to side frame member301 via tubular stud or extension 308. The second pivoting linkage 334is pivotally coupled to side through member 301 via tubular stud orextension 312. A compression plate 332 is provided for additionalstability and is coupled to side frame member 301 via tubular studs orextensions 308 and 312 and pivot stop member 310.

Resilient extension springs 344 and 346 are provided between side framemember 301 and first pivoting linkage 319. In this regard, spring 344has a first connection to frame member 301 via bracket 314 and a secondconnection to first pivoting linkage 319 via bracket 330. Spring 346 hasa first connection to frame member 301 via bracket 316 and a secondconnection to first pivoting linkage 319 via bracket 348. As will bedescribed in more detail, extension springs 344 and 346 are connected tofirst pivoting linkage 319 on either side of the linkages pivotalconnection to side frame member 301 and provide a unidirectional biasforce around the first pivoting linkage 319 pivotal coupling to sideframe member 301. Alternatively, resilient elastomeric members can beintegrated into the pivotal coupling between first pivoting linkage 319and side frame member 301. Similarly, resilient elastomeric members canbe integrated into the pivotal coupling between second pivoting linkage334 and side frame member 301. Such resilient elastomeric members can be“Rosta”-type bearings or other similar structures.

A front caster assembly 335 is pivotally coupled to each of the firstand second pivoting linkages 319 and 334. In this regard, front casterassembly 335 has an integral head tube/bracket 336 for receiving acaster fork 337 and making the aforementioned pivotal couplings tolinkages 319 and 334. These pivotal couplings to linkages 319 and 334are facilitated by first and second holes 338 and 340 in headtube/bracket 336 and corresponding tubular formations in first andsecond pivoting linkages 319 and 334. A rear caster is attached to sideframe assembly 301 via rear caster fork 342, which is received insub-frame member 318.

Configured as such, first and second pivoting linkages 319 and 334 pivotwith respect to side frame member 301. Moreover, front caster assembly335 undergoes spatial displacement with the pivotal movement of firstand second pivoting linkages 319 and 334. The rear caster wheel and fork342 are generally not affected by the pivotal movement of first andsecond pivoting linkages 319 and 334.

Referring now to FIG. 4, an outer side elevational view of side frameassembly 202 is shown under static conditions (i.e., the wheelchair isstanding still or neither accelerating or decelerating). Drive wheel 206is only partially shown so to not obscure the relevant components ofside frame assembly 202. In this state, all wheels including the drivewheels and front and rear caster wheels are in contact and maintaincontact with the ground or other riding surface.

Referring now to FIG. 5, an inner side elevational view of side frameassembly 202 is shown as the wheelchair traverses an elevated obstacle.The component displacement shown in FIG. 5 normally occurs when thewheelchair is quickly accelerated forward to traverse an obstacle suchas curb 500. For purposes of the present discussion, the pivotalcoupling between first pivoting linkage 319 and side frame member 301 isdesignated by pivot P1. Similarly, the pivotal coupling between thesecond pivoting linkage 334 and side frame member 301 is designated bypivot P2. In relationship to each other, it can be seen that pivot P2 isbelow and laterally offset from pivot P1 in a direction toward the frontcaster. In other words, pivot P2 is laterally closer to front casterassembly 335 than is pivot P1. In combination with the respectiveoverall lengths of first and second pivoting linkages 319 and 334, thisconfiguration provides the dual functions of lifting and retracting thefront caster assembly 335 away from the obstacle to be traversed andinward toward the wheelchair.

In this regard, when the wheelchair is accelerated forward by a highrate, the resulting moment arm generated by the drive wheel 206 willexceed the resultant moment arm generated by springs 344 and 346. Thiscauses first pivoting linkage 319 to pivot or rotate in a clockwisedirection about pivot P1 thereby raising front caster assembly 335. Thismotion also causes second pivoting linkage 334 to undergo pivotalmotion. The resulting effect of second pivoting linkage 334 motion is tocause front caster assembly 335 to pivot about its pivotal coupling 338to first pivoting linkage 319. This pivotal movement causes front casterassembly 335 to be drawn inward toward the wheelchair itself and awayfrom the obstacle 500 being traversed. The maximum amount of pivotalmovement is limited by stop 310, which physically engages side framemember 301 sub-linkage 320. The same effect described above is achievedshould side frame assembly 202 be driven directly over obstacle 500.Once the resultant movement arm generated by drive wheel 206 is lessthan the resultant movement arm generated by springs 344 and 346 withrespect to pivot P1 front caster assembly 335 is lowered.

Referring now to FIG. 6, an inner side elevational view of side frameassembly 202 is shown as the wheelchair traverses descends an obstacle600. In this regard, the resultant moment arm generated by springs 344and 346 is greater than any other moment arm around pivot P1. Thiscauses first pivoting linkage 319 to rotate counter-clockwise and tolower the front caster assembly 335 on the lower supporting or ridingsurface. In this regard, the respective position of pivot P2 and theoverall length of second pivoting linkage 334 compared to the positionof pivot P1 and the overall length of first pivoting linkage 319 providefor front caster assembly 335 to descend to the lower supportingsurface. Concurrently therewith, the pivotal motion of second pivotinglinkage 334 causes front caster assembly 335 to pivot about its pivotalcoupling 338 to first pivoting linkage 319. This motion causes frontcaster assembly 335 to extend forward. The combined effect of loweringand extending front caster assembly 335 provide the wheelchair withgreater stability when descending a obstacle because the wheelchair issooner and longer in contact with the differing elevations thatrepresent the obstacle. The maximum pivotal movement is once againlimited by stop 310, which physically engages side frame member 301sub-linkage 322 in this scenario.

Hence, the present invention facilitates the traversing of obstacles andrough terrain by allowing for the vertical and lateral movement of oneor more front caster assemblies.

While the present invention has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. For example, a plurality of casters can beused instead of one caster, the casters can be coupled to the pivot armsvia shock absorbing fork assemblies, and the specific locations of thepivotal couplings can be modified so long as the above-described overallrelationships are maintained. Therefore, the invention, in its broaderaspects, is not limited to the specific details, the representativeapparatus, and illustrative examples shown and described. Accordingly,departures can be made from such details without departing from thespirit or scope of the applicant's general inventive concept.

1. A wheelchair comprising: a frame; a pivoting drive assembly thatincludes: a drive wheel; a motor drive connected to the drive wheel; anda first pivoting linkage fixedly attached to the motor drive, whereinthe pivoting drive assembly is pivotally coupled to the frame at a firstframe pivot axis such that the drive wheel, motor drive, and firstpivoting linkage pivot about the first frame pivot axis as a unit; asecond pivoting linkage pivotally coupled to the frame at a second framepivot axis; and a front caster assembly, wherein the first pivotinglinkage is pivotally coupled to the front caster assembly at a firstfront caster pivot axis and the second pivoting linkage is pivotallycoupled to the front caster assembly at a second front caster pivotaxis.
 2. The wheelchair of claim 1 wherein the motor drive is fixedlyconnected to a mounting bracket of the first pivoting linkage.
 3. Thewheelchair of claim 1 wherein the motor drive is fixedly connected tothe first pivoting linkage at a position below the first pivotinglinkage.
 4. The wheelchair of claim 1 wherein the first frame pivot axisis between an axis of rotation of the drive wheel and the front casterassembly.
 5. The wheelchair of claim 1 wherein the second frame pivotaxis is between the first frame pivot axis and the front casterassembly.
 6. The wheelchair of claim 1 wherein a distance between thefirst frame pivot axis and the first front caster pivot axis is greaterthan a distance between the second frame pivot axis and the second frontcaster pivot axis.
 7. The wheelchair of claim 1 further comprising aspring connected to the first pivoting linkage and to the frame at aposition that is between the first pivoting linkage and the rear caster.8. The wheelchair of claim 7 wherein the spring biases a front caster ofthe front caster assembly downward.
 9. The wheelchair of claim 1 whereintorque applied to the drive wheel urges the front caster assembly awayfrom a support surface.
 10. The wheelchair of claim 1 wherein torqueapplied to the drive wheel lifts the front caster assembly off of asupport surface.
 11. The wheelchair of claim 1 further comprising atleast one rear caster coupled to the frame.
 12. A wheelchair comprising:a frame; first and second independent pivoting assemblies coupled toopposite sides of the frame, wherein each of the first and secondpivoting assemblies includes: a drive wheel; a motor drive connected tothe drive wheel; a first pivoting linkage fixedly attached to the motordrive, wherein the first pivoting linkage is pivotally coupled to theframe at a first frame pivot axis such that the drive wheel, motordrive, and first pivoting linkage pivot about the first frame pivot axisas a unit; a second pivoting linkage pivotally coupled to the frame at asecond frame pivot axis; and a front caster assembly, wherein the firstpivoting linkage is pivotally coupled to the front caster assembly at afirst front caster pivot axis and the second pivoting linkage ispivotally coupled to the front caster assembly at a second front casterpivot axis.
 13. The wheelchair of claim 13 wherein the motor drive isfixedly connected to a mounting bracket of the first pivoting linkage.14. The wheelchair of claim 13 wherein the motor drive is fixedlyconnected to the first pivoting linkage at a position below the firstpivoting linkage.
 15. The wheelchair of claim 13 wherein the first framepivot axis is between an axis of rotation of the drive wheel and thefront caster assembly.
 16. The wheelchair of claim 13 wherein the secondframe pivot axis is between the first frame pivot axis and the frontcaster assembly.
 17. The wheelchair of claim 13 wherein a distancebetween the first frame pivot axis and the first front caster pivot axisis greater than a distance between the second frame pivot axis and thesecond front caster pivot axis.
 18. The wheelchair of claim 13 furthercomprising a spring connected to the first pivoting linkage and to theframe at a position that is between the first pivoting linkage and therear caster.
 19. The wheelchair of claim 18 wherein the spring biases afront caster of the front caster assembly downward.
 20. The wheelchairof claim 13 wherein torque applied to the drive wheel urges the frontcaster assembly away from a support surface.
 21. The wheelchair of claim13 wherein torque applied to the drive wheel lifts the front casterassembly off of a support surface.
 22. The wheelchair of claim 13further comprising at least one rear caster coupled to the frame.